Field of the Invention
The present arrangement relates to fiber optic connectors. More particularly, the present arrangement relates to fiber optic connectors with reversible polarity.
Description of the Related Art
In the area of fiber optic connections, typical fiber optic systems usually have to establish a bi-directional pathway between a transmitter port on a first element and receiver port on a second element and vise versa. See for example schematic FIG. 1. In order for such a bi-directional systems to function, it is a requirement that one end of a fiber be connected to the light emitting source of a first equipment, often a type of laser or light emitting diode, and the other end connected to a receiver port on a second equipment. For the second fiber in the bi-directional pathway, the other fiber needs to be connected to the light source on the second equipment and, at the other end, the receiver port of the first equipment.
Fiber optic connectors used for larger high-speed fiber optic systems often use multi-fiber cables supporting many bi-directional pathways. In one example the cables typically have 12 fibers in the cable, with the corresponding connectors for such cables housing multiple fiber optic members within the same connector body. Such a twelve fiber arrangement can support six of such bi-directional (duplex) pathways.
These connectors used for such high-speed fiber optic systems often employ what are termed multiple fiber optic members, called MPO (Multiple-Fiber Push-On/Pull-off) connectors and they typically support the twelve fiber (six duplex channel) arrangements within the same connector body.
Using FIG. 1 showing a single two way channel, there can be many segments of fibers between two components, each representing a fiber optic cable with a connector. In some cases, between segments, the fibers in the connector of a first segment pass directly across to the fibers of the second segment. However, in some cases, in order for the transmission signal to end up at the correct receiver port, at least one segment connection, the connectors must have the pin/fiber input/output on one side flipped so that the transmission signal exits on the other fiber in the channel.
This situation is referred to as connector “polarity” for each segment.
A fiber cable segment with two connectors at either end that result in the same polarity across the segment is referred to as method A and a fiber cable segment with two connectors at either end that result in a flip in the polarity across the segment is referred to as method B. In FIG. 1, the first four segments are method A polarity, the fifth segment is method B polarity exhibiting a flip in the light pathways across the two fibers.
Depending on the various fiber optic equipment arrangements, in the prior art, to make the correct connections, the installer selects cable segments (i.e. pre-terminated lengths of cable) that have the correct polarity. The openings in the transceivers and adapters have a key opening and the corresponding MPO connectors on the cable have a key (see e.g. the trapezoid shaped “key” element. The MPO connectors will only fit into the slot with the key in the right space. For example, if an installer requires a polarity A connection, the two connectors on the end will have keys that force their insertion into the desired transceivers/adapters with the resulting connection being that shown in FIGS. 2A and 2B. If an installer requires a polarity B connection (“flip”), the two connectors on the end will have keys that force their insertion into the desired transceivers/adapters with the resulting connection being that shown in FIGS. 2C and 2D. As such bi-directional pathways connected with pre-terminated cables using MPO connectors, must still eventually result in one end of a fiber being connected to a source and the other end connected to a receiver and vice versa for each bi-directional pathway supported. As shown in FIGS. 2A and 2B, the top FIGS. 2A and 2B show Method A polarity where the blue fiber starts on position 1 on one connector on one side of the segment and is at the same location (position 1) on the other connector on the other side of the segment. This method A polarity arrangement would be a straight forward connection that passes the same connection polarity to the next segment of the installation.
FIGS. 2C and 2D show Method B polarity where the blue fiber starts on position 1 on one connector on one side of the segment and is at the opposite location (position 12) on the other connector on the other side of the segment. With Method B polarity the remaining fibers in the connector on the second side of the segment are all also transposed in position vis-à-vis the first connector. The management of connections in such MPO connectors between sources and receivers and the polarity of such connections is described in the standard TIA-568-C.3. This method B polarity arrangement would be a connection that reverses the connection polarity going forward to the next segment of the installation.
As shown in FIG. 1, in order for the light signal from one source to reach a receiver at the other end there typically must be an odd number of ‘flips’ in the cabling, where a ‘flip’ indicates a method B polarity segment, so that the fiber in connector position 1 is connected to position 2 on the other side, the fiber in connector position 2 is connected to position 1 on the other side, etc.
These flips can be achieved via individual fiber assemblies and/or in the adapters that connect different fiber optic cabling segments together for example as shown in the basic design in FIG. 1 at segment 5. However, since fiber optic networks are dynamic environments, connections are often added or subtracted and the number of required flips changes within the cabling arrangement between equipment. Ensuring that there are an odd number of flips then requires one or more of the fiber optic assemblies' polarity to be changed as the connections are added or subtracted. This requires the installers and/or end users to stock connection cables with MPO type connectors at either end of both type A and type B polarities and lengths for every possible network configuration, given that connection cables are pre-terminated with MPO type connectors of a fixed polarity. For example, the connection cables are typically pre-terminated with the MPO connectors and associated keying arrangement meaning that a particular patch cable is either a polarity A type cable or a polarity B type cable. One type of cord (e.g. type A) cannot be easily converted to a type B type cord.
When preparing an initial fiber optic arrangement (e.g. transceivers, adapter and patch cables) at a given location, the required polarity of fiber optic segments/cable connections is carefully considered during the design phase and is generally fixed upon completion because, as noted above, the patch cords come pre-terminated and the polarity of the connector(s) is set at manufacture. Returning to the concept of the relative arrangement of the keys on the connectors for fixing the polarity type of the patch cords, a patch cord having connectors for its end set at a first polarity (i.e. method A or method B) can only be used for example in FIG. 1 at certain segment locations. However, if for any reason the configuration changed, as will be explained in more detail below, the installer may require a new patch cord, possibly of a different length, and having its two connectors set at a different polarity. Consequently, end users must carry a large inventory of pre-terminated assemblies or order additional parts to allow for reconfigurations of the network topology.
As noted above, the polarity of an MPO (Multiple-Fiber Push-On/Pull-off) style connector, whether it be method A or method B is determined by the relationship between the fibers and a “key” on the connector body, which is why polarity is sometimes referred to as “keying.”
Prior art FIG. 3 shows a perspective view of a standard prior art MPO connector (shown in FIGS. 2A-2D in front axial direction) that has a single fixed key on its body. A cable having such a MPO type connection pre-terminated thereon will thus have its polarity set at the time of manufacture.
Some prior art arrangements have the ability to change the key/polarity of the connector by allowing for a changing of the key arrangement on the connector from one side to the other (i.e. if done on one side of a cable it would reverse the pre-terminated cable from type A polarity to type B polarity), these solutions require the disassembling and reassembling of connectors or the purchase of new connectors. This solution would allow an existing connection pre-terminated cable to be converted from one polarity to another to be re-used, for example when an existing fiber optic arrangement is re-arranged and requires a differ polarity connection. However, such connectors that require complicated means for changing the key/polarity setting on a connection, is time consuming and increases labor costs and/or material costs associated with these modifications.